Spirit Stills and Reboilers?

[Fredrika Gross]

All,

I recently visited a couple of microdistilleries that had two-step
distilling processes.

The first step was a conventional distillation in a wash still, the second
was a surprise.

One distillery used what they called a "reboiler" for the second
distillation.  This "reboiler" did not use any source of heat other than the
distillate from the first step.

The other distillery used an alembic still for the second distillation.
Again, there was no additional heat for the second distillation.

Up to now, every distillery I've seen added heat to the spirit still to
accomplish a second distillation.  Can any of the MALTS-L experts point me
to something that discusses how this second distillation is accomplished
without additional heat (it doesn't need to be too technical)?  I don't
believe either distillery was using vacuum distillation.

(I've already looked in "Whisky: Technology, Production and Marketing",
BTW.)

Thanks,

Brian Gross

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